#1 Heels' credibility is ruined
The job of heels is to be hated and to make the babyface look better or gain more credibility. The roster is jam-packed with top heels such as Drew McIntyre, Bobby Lashley and Baron Corbin. All three of these men could give Rollins a run for his money and easily take the fall without hurting their position in the roster.
Right now, a face vs face match with three weeks left to build doesn't really sound intriguing. WWE would do what they usually do and book them in Tag Team Matches against the heels of the company or cut promos that would portray each one's sportsmanship.
When one of them loses at MITB, the only way to make the feud last would be to turn the loser heel and from the most recent example, Shinsuke Nakamura, one must fear what the future holds for Rollins or Styles if they turn heel.
Also, not to forget the immense NXT talent that the main roster has right now. These Superstars could have easily been picked to become Rollins' first challenger and a loss wouldn't have made them look weak either.